New here, any help appreciated. Been foiling for 3 years now. Does anyone have any experience using Chinook 10" fin boxes for a sliding 90mm (LF) flange mount? They have 8mm flange nuts, but the chinook folks say they sell these to foil board builders, but do not provide installation advice. My plan is I have a 5'2" epoxy naish surfboard that I want to put an adjustable track on. Having read every post I can find, the tracks set into the board with a glass or carbon wrap from the bottom skin back to the bottom skin to take the upward forces, and tie the top of the tracks to the top deck as well seems to be what is needed as just sinking it in epoxy might be too weak.
I don't want to add too much weight but don't want a failure either.
Questions.

Has anyone used Chinook boxs, or is there a better choice?

Putting tracks in, how much reinforcement is needed, and of what material?

Do I need to add stringers going forward, if so what and how far?

I could just through bolt with appropriate compression block, but I am sucking in my friends to foiling because it is so much fun, and weights have varied from 50 to 90 kg and sliding track might help the learning curve.

If the naish is an eps board then it's a define no no just sinking the boxes in ..... you must add high density foam and then sink in the boxes into that. Bridging the top and bottom skins increases the strength dramatically but at a cost of weight.

If you use boxes. You have to drop in HD foam from bottom to deck laminations. Then put boxes into that, then re laminate over it on bottom. You can do it all from the bottom.
It's a big job. Buy a North, naish or shinn foil board ( among others) instead

Blackrat and TomW, thanks for your input!
I understand the mast base localized loads have to be compensated for by either spreading the load (like the FoilMount glue on), or using higher strength material around the tracks.

Does anyone have good experience with Chinook fin boxes? Has anyone tried a foilmount? By the time you add up tracks, hd foam, carbon and epoxy, it's about 150 bucks, about the FoilMount cost. Tracks would not be a wart on the bottom of the board, and there is always the satisfaction of diy. I could buy another board already set up with tracks, but I like how this one performs.

Would appreciate if someone has used the Chinook tracks, how much reinforcement was used to be a success. Thanks!

I used Chinook boxes couple of time for foil mount. no problem at all! just follow TomW advice. Couple of layer of carbon at the bottom is enough to hold the plate. Note, that there are two king of chinook boxes. one is very heave (180) and another is 120 gr , I guess. both are strong enough for foil boards

Thanks, that's actually a really good suggestion! The weight of 12 ea 20mm epoxy cores drilled out to 8mm is less than the weight of a track and is the same amount of adjustment. Any suggestions about how far from the back of a pintail board to start the mast adjustment? 6 or 8 inches for the back of the flange sound about right? Thanks, Robert

Thanks, that's actually a really good suggestion! The weight of 12 ea 20mm epoxy cores drilled out to 8mm is less than the weight of a track and is the same amount of adjustment. Any suggestions about how far from the back of a pintail board to start the mast adjustment? 6 or 8 inches for the back of the flange sound about right? Thanks, Robert

Depends on the board, and foil, and rider. Figure out where your rear foot belongs on surfboard, figure out where your foil belongs in relationship to rear foot (on normal foil board), drill there. Drill holes over-sized and use big washers. I’d be concerned about the deck snapping though, especially if giving to beginners who are going to porpoise it a lot, might consider a bit of unidirectional carbon along deck, and a layer of carbon under rear foot, where the holes will be.

Fair warning, I drilled holes in a surfboard, and while it worked, I ended up filling them in and using a designated foil board instead, I did not like the holes there when using the board without the foil, water would splash through the holes while riding, which is a lot more annoying than it sounds.